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Introduction

Structured storage is something which, when done using the plain Windows API, seems overly complicated; much more so than is needed. The aim of this article is to briefly introduce you to the concepts behind structured storage, and then provide a helper class to simplify its usage.

The idea behind structured storage is that a single file can itself contain a basic filing system. Its main reason for existence was to help with OLE documents: embedded objects are simply save as separate 'streams' within the single file. Here is a diagram which illustrates this concept:

STRUCTURED STORAGE FILE

First_stream
Second_stream
A_storage
- Stream_in_stg

Although this technology is primarily for use in OLE, it can be put to other uses. In order to help you access the functionality of this powerful tool easily, I have created a helper class, namely CSSFile, to aid in the creation, and modification of structured storage files.

Updates

If you have used this class previously, you will most likely wish to update your code to use the latest version. Here are the main differences (note that the interface remains the same):

The use of const references for faster parameter passing
Quicker operation as a result of reduced 'waste' code
Removal of un-needed variables and code from the class
Better arrangement of source and header files.
Integration of help into the article rather than as a HTML Help download.
Proper UNICODE awareness

Usage of the class

Whilst the class is fairly straightforward, I have listed the functions and their interfaces below to aid your usage of the class:

Function: CreateSSFile(...)

Parameters

filename - the name of the file to be created

mode - the mode of access for the file

Return value

'true' if the file was successfully created

Function: OpenSSFile(...)

Parameters

filename - the name of the file to open

mode - the mode of access for the file

Return value

'true' if the file was successfully opened

Function: Attach(...)

Parameters

pNews - the storage this object should hook

Return value

The previous storage being managed by the object

Function: Detach(...)

No Parameters

Return value

The previous storage being managed by the object

Function: Close()

No Parameters

No Return value

Function: CreateStorage(...)

Parameters

name - the name of the storage to create (will be created within the current path inside the root storage)

enter - enter the storage after creation?

mode - the mode of access for the storage

Return value

'true' if the storage was successfully created

Function: EnterStorage(...)

Parameters

name - the name of the storage to open

mode - the mode of access for the storage

Return value

'true' if the storage was successfully opened

Function: ExitStorage(...)

No Parameters

Return value

'true' if the storage path was moved up a level

Function: CreateStream(...)

Parameters

name - the name of the stream to create

sf - a COleStreamFile into which the stream is opened

mode - the mode of access for the stream

Return value

'true' if the stream was successfully created

Function: OpenStream(...)

Parameters

name - the name of the stream to open

sf - a COleStreamFile into which the stream is opened

mode - the mode of access for the stream

Return value

'true' if the stream was successfully opened

Function: DestroyElement(...)

Parameters

name - the name of the element to destroy

Return value

'true' if the element was successfully destroyed

Function: GetRootStorage()

No Parameters

Return value

The root of the currently open storage

Function: GetCurrentStorage()

No Parameters

Return value

The currently open storage

Function: IsOpen()

No Parameters

Return value

Whether a file is currently being managed by the object

Function: GetFilename()

No Parameters

Return value

The filename of the root storage

Function: GetPath(...)

Parameters

SepChar - the character to be used to separate the paths in the storages (i.e. Windows uses '\' for standard file system paths).

Return value

The current path within the storage (including the filename of the root storage).

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Andrew Peace

Andrew is currently a student at the University of Cambridge, working towards a degree in Computer Science. The word 'working' is used here in a vague sense, with the hope that the reader will realise that the same sentence contained the word 'student'.

Aside from computing he has a strong interest in music, and enjoys the outdoors, particularly when the weather permits going out in them... To Andrew, cycling is fun, sailing is more fun, and the odd camping trip and walk is certainly what the doctor ordered.

In terms of programming experience, he first started writing programs for the Commodore Amiga using BASIC, after which he learned the joys of C and has never looked back. Since, he has added C++ and C# to his repotoire, along with a bunch of other crazy languages like ML that they like to teach in college.

Location:

United Kingdom

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Wrapped into a dll to get info from outlook msg files

Calvin Streeting

12:32 10 Jan '07

Hi..
I have wrapped this code into a dll that parses outlook msg files without outlook and was wondering on how you feel about me posting up the code (maybe even on sourceforge, and my home page) as i have found many people looking for this. but as far i cannot find a open source version anywhere (As my code only sits on top of yours i have not had to make any ammendments to your code). by posting code on sourceforge i could get others to help flesh out the Dll bit (no need to touch your code as it works fine Smile

) as this is my first ever c++ code.

Re: Wrapped into a dll to get info from outlook msg files

Wojan

4:13 11 Jan '07

Calvin, Do you program in C# as well? I am needing to be able to extract embedded files in Office documents and .msg files. I think your .msg dll might work for this but was wondering if you could port it to C#? Thanks!!!! Scott
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

14:13 11 Jan '07

Hi...

The Dll is written in C++. i am not very experiance in C (this was my first sucses in c, bit more than a "hello world" app Smile

).

I think this could be raly usefull for poeple. hence me asking the author for permision to include on sourcforge... do you know c and if so what do you think about working on it with me on sourceforge.... and making it publicaly avaliable and open source...

It is written in vc6.0 and i need help prosesing the date formats in c which at the moment i am doing in vb as this is a language i know realy well..

Re: Wrapped into a dll to get info from outlook msg files

Wojan

15:51 11 Jan '07

No, I don't know C or C++, only C#. The implementation of the structured storage format is what is giving me a hard time. It's very poorly put together!
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

22:54 11 Jan '07

Ok that new to me i thought they where the same language .. i take that c# can call dll's, I could give you my a copy of my code but this is only writen to deal with msg files and only the things i need to get (sender name, sender email, to name, date, subject, body, attachment count etc..)
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Re: Wrapped into a dll to get info from outlook msg files

Wojan

3:46 12 Jan '07

C++ is object oriented C. C# is a completely different language. If you could send me your code, that would be great! Thanks!
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

4:51 12 Jan '07

OK... i will Email it to you when i get home tonight
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

13:53 12 Jan '07

Hi Wojan I need your email address to send you the files
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Re: Wrapped into a dll to get info from outlook msg files

Wojan

15:20 12 Jan '07

guidokj rocketmail.com
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Re: Wrapped into a dll to get info from outlook msg files

Andrew Peace

12:32 15 Jan '07

Hi, Please do go ahead and publish the code to your homepage or SourceForge - as long as you leave my copyright headers on the files that I contributed I am happy for you to do this. Thanks, and I'm glad you found the code useful. -- Andrew.
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

14:28 15 Jan '07

Many thanks, I have applied for a Sourceforge project (my first) and i will keep you posted
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Re: Wrapped into a dll to get info from outlook msg files

Calvin Streeting

15:07 17 Jan '07

Ok I got the project registerd on sourcforge and for your information here is the url https://sourceforge.net/projects/ssfiledll/ many thanks p.s now i need to see if i can get to the IMessage stored in outlook msg files and thus get more information (oh and learn more c++ )
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Re: Wrapped into a dll to get info from outlook msg files

RahulOP

2:42 19 Jan '07

Hi,
I posted my message on the VC++ Message Board as well but I got no response so re-posting here on the off chance that someone might reply Smile

I'm trying to add HTML(associated JPEGs are in a separate folder) and MP3 files to a dll and then use them in another dialog based app. Now, thanks to CP i know how to add Jpegs to a DLL and call them but am completely stumped as to how to call the HTML or MP3 via ActiveX(MS WebBrowser Control and W.Media Player respectively)

Any clues?

How to write doc file

vbhole

0:18 10 Sep '05

How can we use the above code write the word DOC programatically??
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how to rename Ele Element

riverclod

18:47 15 May '05

how to rename Ele Element
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Word OleLoad (Structured Storage) Problem !

vishalmore

19:07 26 Nov '04

Hello, I have created a structured storage in memory and using "OleLoad" etc. I can open that successfully in Word inside my control. However there is temporary ~WRO0000.doc file created in TEMP folder that I dont want to be created. I will appriciate if any body help me in disabling this temp file creation. Thank you, Vishal
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Re: Word OleLoad (Structured Storage) Problem !

Andrew Peace

2:47 27 Nov '04

I'm not an expert in OLE, but I would suggest that it is impossible to prevent the file from being generated - it is Microsoft Word itself that generates those files, if you open a .doc file in Word you get the same effect. Hopefully someone else will have a better answer for you . -- Andrew.
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Re: Word OleLoad (Structured Storage) Problem !

vishalmore

3:22 27 Nov '04

Hi Andrew,

If we open normal .doc file in MS-WORD it does not create "~WR0XXXX.doc" file, instead it creates a "~wrdxxxx.tmp". Please refer to following link
from microsoft it says all about ".tmp" file created by word.

http://support.microsoft.com/default.aspx?scid=kb;en-us;211632[^]

In my case word is creating not just a ".tmp" file, its creating
"~WR0XXXX.doc" file which has original content of the word file and ".tmp" file are not in readable format. I want to prevent this "~WR0XXXX.doc" file
creation at any cost !

I will appriciate it, if any body could take me out of the situation !

Cry

Thank you !

Vishal

2.00/5 (1 vote)

Optimizing file size...

Tamer

22:49 13 Oct '04

First of all, this is a very nice work, you're great! i noticed that when i have a SS file with certain size and when i destory all the elements in the SS file, the file will still have the same size. Can you on how to optimize this file size??
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How to save HTMLs into single?

Alick Xiong

23:47 18 Jun '04

I have just read your article for I have been looking for some information to do my work. I have to save several HTMLs not only one into a single file without any source(jpg,gif,etc.)lost. I found Structured Storage on the web which I have never used before.How to use this for my work?First,I must save several HTMLs into a single file such as *.abc;Second,I can reload the *.abc,then I can read the htmls in a htmlview in my project. I was confused.
Could you give me some ideas ? Or a example would be nice.Thank you very much!

Alick

Re: How to save HTMLs into single?

Peter Weyzen

16:49 23 Aug '04

Your HTML consists of a number of different asset types:
* HTML source file
* image assets (JPG,GIF)
* possible other stuff

To save all this:
1) Create the DOC file
2) Open a stream for the HTML, call it "HTML"
3) Save the HTML contents into that stream
4) For each additional asset:
a. open a stream
b. name it the same as the asset (filename.gif or filename.jpg)
c. save the contents of that asset
d. close the stream

Now you've got one physical file, with each of these elements nicely segmented into their own streams.

Docfiles are an easy way to combine multiple different data/file types into a single physical file.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Peter Weyzen
Staff Engineer
Santa Cruz Networks

Re: How to save HTMLs into single?

anoymous

2:33 12 Mar '05

Yes,you are right. we can save html into a single file in your way. but the saved file can't be opened in IE. Do you think so? I think this is the real problem . Any ideas? Thank you very much.
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Re: How to save HTMLs into single?

Peter Weyzen

13:17 12 Mar '05

oh, sorry. I guess I missed the point of your post. IE won't be able to open that file. I thought you just wanted to store a bunch of assets into a single file. Do some research on mail formats. They can send text and pictures in the same file and have it properly viewed. -p `~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Peter Weyzen Staff Engineer Santa Cruz Networks`
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IViewObject2::Draw()'s problem?

ArnoldZ

20:28 20 Oct '03

If insert OLE object is OT_STATIC type, when you save and reopen it, why ask "save or not" even if nothig chang. Because after call IOleObject::Draw, COleClientItem::IsModified return true. Why? Example:Make a container with MFC, and insert a BMP picture, save and reopen.
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bug

Gao yihong

18:36 9 Oct '03

A storage can not be more than 31 chars!
Sign In·View Thread·PermaLink	5.00/5 (1 vote)

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